@misc{indiciae5de1970c970f,
  title = {Map showing areas that correlate with subsidence events due to underground mining of the Pittsburgh and Upper Freeport coal beds, Allegheny, Washington, and Westmoreland counties, Pennsylvania},
  author = {K.O. Bushnell},
  year = {1975},
  doi = {10.3133/mf693c},
  url = {https://pubs.usgs.gov/publication/mf693C},
  note = {Source identifier: mf693C}
}